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8 (No MbdeLL A J. I. SABIN.

TELEPHONE EXCHANGE SYSTEM AND APPARATUS THEREFOR. N 249,262. I PatentedNov. 8,1881.

A A A A in UNITED STATES PATENT OFFrcE.

, JOHN I. SABIN, OF SAN FRANCISCO, CALIFORNIA, ASSIGNOR TO THE AMERICANBELL TELEPHONE COMPANY, OF BOSTON, MASS.

TELEPHONE-EXCHANGE SYSTEM AND APPARATUS THEREFOR.

SPECIFICATION forming part of Letters Patent No. 249,262, dated.November8, 1881.

Application filed April 26, 1881. (No model.)

To all whom it may concern:

substations situated atvarious points within the geographical districtwhich the central sta tion is designed to serve. andarrangementofthelines, commutators, and apparatus in the exchange orcentral station is suchthat any two substations within the district mayat a moments notice be placed in direct telegraphic or telephoniccommunication by the act of an operator or attendant who is keptconstantly on duty at the central station,

.and who, upon being notified to do so by a subscriber or other personat asubstation, unites the terminals of the twolines which are desiredto be connected together by means of suitable switching or connectingdevices provided for. this purpose.

i The present invention consists, mainly, in certain improvements uponasystem and apparatus of this character shown and described inmy formerLetters Patentof March 29, 1881, No. 239,557, whereby the connection anddisconnection of lines may be effected with greater convenience andfacility than has heretofore been possible, especially in exchangeswhere a very large nnmberof wires are assembled together. i

The particular combinations of mechanism which constitute thesubject-matter hereinclaimed as new are more particularly designated inthe claims at'the end of this specificattionr p f 'In the accompanyingdrawings, Figure l is i a diagram illustrating the organization of acentral or exchange station, showing the relations of the various partsof the apparatus to each other and illustrating the method of operation.Fig.2 is a detailed sectional viewof the switch-plug or connector.

The organization Referringto Fig. 1, A represents a group of line-wiresentering the central or exchange station. Each wire extends to theresidence or place of business of an individual subscriber within thedistrict, or, as it will be hereinafter termed,t0asubstation.Thedrawingsshow but four of these lines, which is asufficient number forthe purpose of illustration, but the number will ordinarily be muchgreater than this, and in important stations there may be severalhundreds of such lines converging to the exchange as a common center. Atthe distant end of each substation-line is placed a signal apparatus,which may consist of a battery and key or of a magneto-electricgenerator, together with a transmitting and receiving telephone. Allthese several devices and their arrangement at the substation, inconnection with the line, are well known, and therefore do not require.detailed description.

B and B are two duplicate switch-boards,

very great a single switch-board, as '13, having a .number of separatecommutators upon it equal in number to the lines to be provided for,will be sufficient; but when the number of operator, then a duplicateswitch-board, as B,

is provided,.a-t which a second attendant may be stationed,'and in thismanner the labor may be subdivided to any required extent as the numberof lines increases. Each line-wire is connected with its correspondingcommutator in each switch-board, and each commutator should bemarkedwith a number corresponding to the number designatingthc line towhich it appertains. The upper section, a, of each lines entering theexchange becomes greater than can be promptly attended toby a singlecommutator isiconnected with its correspond ing line-wire. 'The lowerright-hand section,

0, of each commutator of the switch-board B is united to a common wire,(I, which extends to a local battery, E, the other terminal of which isconnected directly to the ground at G. In like manner the lowerright-hand section of each commutator of the switch-board B is connectedby a com mon wire, '01, to another local battery, E, and thence to theground at G. A single local battery might serve for two or moreswitches; but it is usually preferable to employ aseparate battery foreach switch.

The lower left-hand section, I), of each commutator is connected by aspecial electromagnet, H, by means of a wire, I), and thence directly tothe ground at G by means of wire g. Each separate line is provided withan electromagnet, F, the office of which is to operate a switch for thepurpose of directing the circuit of said line through areceiving-telephone, at which an attendant is stationed, who is able tohear what is said by the person at the substation. The'arrangement ofthe connections of each separate main circuit in the central office isthe same, and will be most readily understood by tracing the course ofsome one line-for example, line No. 143 of the group entering thestation at A. This line connects by means of a branch wire with theupper section of the commutator 143 in switch B, and inlike manner withthe upper section of the commutator 143 of switch B, and from thence itproceeds to the armature-lever h of its corresponding automaticswitching device, by means of which the main-line circuit is connectedwith one or the other of two branch lines, as hereinafter explained.When all the parts are in their normal position of rest the arma- I inthe series.

terminating in a metallic peg, p, with a suit ture-lever h is held inplace against the tension of the springh by means of a latch or detent,f, formed upon the extremity of the armature f of a secondelectromagnet, F. When all the parts are in the positionjust describedthe circuit of the main line 143 passes through the armature-lever It tothe armature-lever f,

with which it is in contact, and thence by wire 9 through theelectro-magnet F and to the earth at Gr- Hence, when an electric currentfrom the substation traverses line 143, the electro-magnet F, andearth-circuit g to ground G, the said magnet F lifts its armature f andreleases the armature h. Thelatter is instantly drawn back by the springh and the connection between the main line and the branch or earthcircuit 9 is interrupted and a new circuit formed through the branch onby the'armature it coming in contact with the stop h.

o is a normally-open earth-circuit, in which is included areceiving-telephone, T, and this circuit is connected by means ofbranches m m m m with the stops it of every annuneiator r is anotheropen earth-circuit,

able handle, and includingatesting apparatus, R, which may be of anydescription capable of indicating the presence of an electric current inthe wire. I prefer to employ for this purpose an ordinaryelectromagnetic bell, as

shown in the figure, but a galvanometer or any known apparatus servingthe same purpose may be employed.

The connection between two lines entering the central station iseffected by means of an ordinary flexible connection, usually termed aswitch-cord, which is armed at each end with a switch-plug constructedas hereinafter described. A portion of the cord and one of theswitch-plugs is shown in detail in Fig. 2. The handle W of the plug isof a cylindrical form, and made of some insulating material, such ashard rubber. It is provided with a prolongation, w, of smaller diameter.Upon the under side of this prolongation is fastened a metallic plate,2, by means of screws or otherwise, and upon the upper side is fixedanother metallic plate, 3 which is made in the form of a spring, andworks in a groove in the handle of the plug at 12 and is attached ,tothe conducting-cord m at the point of the plug by means of a screw, a,or otherwise. Thus it will be understood that the conducting-cord or isin electrical connection with the upper spring, y, of the plug, whilethe lower plate, 2, is entirely insulated.

The operation of the improved apparatus is as follows: Let it besupposed that a person at the substation of line 143 wishes to be placedin direct communication with the substation of line 141. He firsttransmits a call-signal to the central office, consisting of an electriccurrent which instantly traverses the electromagnet F of the automaticswitch, as previously explained, transfers the connection of the mainline to the branch line m and earthcircuit 0, containing the telephoneT, at which the receiving-operator is stationed. Immediatel y aftertransmitting the call-signal the substation-operator speaks through histelephone, and gives the number or name of his substation-line and thatof the substation-linein this case 141with which he desires con Thiswill be heard by the receiving.

nection. operator, who will then take a switch-cord and insert one ofits plugs in the commutator of line 143 and the other one in commutatorof z, upon the under side of the plug, which'will close a local circuitfrom the battery E through the wire 61 to the section 0 of commutator of143 in switch B, thence to the section b of the same, thence by wire I)!to electro-magnet H, thence by wire g to the other pole of the batteryE. The closing of this local circuitwill armature-lever 7b, being nowheld close to the poles of the local electro-magnet H, is notin con- 35an electric switch or circuit-changer actuattact with-the detent f,consequently the connecting of both mainlines with the earth is therebyinterrupted so long as the local circuit is closed at the switch. 7 i

In case two or more duplicate switch-boards are employed in an exchange,it is necessary, after receiving a call for a connection with aparticular line, to ascertain whether or not that line is already inuse. For this purpose I make useot" the open earth-circuit r andtesting-instrument B, it being only necessary for the operator, beforemaking the connection, to touch the metallic peg p, which is inconnection with the wire 1, to the lower left-hand section of thecommutator of that particular line. If the line is in use a current fromthe local battery E will pass through the testing-instrument and actuateit, because the circuit is already closed by the insertion of aswitch-plug in the correspondingconnectorofone oftbeotherswitches, andthe testing-instrument therefore will respend; but if the line is not inuse no plug will means for automatically restoring the circuit beinserted, and consequently the left-hand section of the commutator willhave no batteryconnection and the testing-instrument willnot respond. Inthis way it may at oncebe ascertained by the operator whether or notthat particular line is in use.

Having now fully described my said invention, and the manner of carryingthe same into effect, what I claim isi i 1. In a system of electricalcommunication, thecombination of two or more switch-boards connectedeach with the several line-circuits entering the central station bybranch wires,

ed by an electro-magnet in a branch circuit normally connected to eachmain circuit and adapted to transfer the main circuit from said branchto a normally-open branch circuit, which includes a telephone ortelephones,

changers and main-line circuits to their normal'positions, and anormally-opentesting-circuit, including an electro-magnetictesting-instrument, with means for connecting the same to'any particularline for the purpose of ascertaining whether such line is already inuse, substantially as described.

2. In a telephone-exchange system, the combination, with amain -linecircuit and an automatic electric switch or circuit-changer in saidcircuit for altering the connections thereof, of

means whereby the electric switch or circuitchanger and the main-linecircuit connections are automatically restored to their normalpositions, said means consisting of an independent circuit normallyopen, an electro-magnt included in said circuit, a circuit-closer, and adouble connector or switch plug, which, when putiinto position forconnecting one line with another, is. adapted to operate saidcircuitcloser, substantially as described.

3. The combination, substantially as hereinbefore setforth, with aline-circuit and automatic electric switch in said circuit for alteringthe connections thereof, of a commutator or switch having threecontacts,one connected to the line, one to the battery and earth, andone to anelectro-magnet acting to restore the automatic switch of saidline to its normal position,'a contact-peg forming the terminal of lmagnetic testing device included in said open earth-circuit,substantiallyas described. 7

5. The combination, with an automatic electric switch or circuit-changeracting to alter the connections of theline on which it is placed, of an.electro-magnet acting by the attraction of'its armature to interruptsaid line and to bring the several parts into position forre-establishing the normal condition of the circuit when the armature isreleased or drawn back,

substantially as described.

6. The combination, with one or more switchboards and lines centeringtherein, of a series ofautomat'ic switches or circuit-changers foraltering the electrical connection of said lines, and a series ofelectro-magnets for restoring the said switches to their normalposition, substantially as and for the purpose set forth.

7. The combination, with one or more switchboards, a series ofline-circui ts connected with said switch-boards, and a series ofautomatic electric switches in said line-circuits, of electricallyoperated devices for restoring said switches to their normal position,and means, as explained, for automatically bringing said devices intoaction in establishing connection onthe switch-board between saidline-circuits, substantially as described.

8. The combination, substantially as hereinbefore set forth, of two ormore main signalingcircuits converging to a common receiving-station,each of said circuits being provided with, first, a branch circuitnormally in electric connection with the main circuit; second, a switchI or'circuit-changer actuated by an electro-magnet included in saidbranch circuit, which, when, thus actuated, transfers the connection ofsaid main circuit to a normally-open earthcircuit, which is common toall the main circuits when thus transferred; and, third,anelectro-magnet in an independent circuit for 'lis'toringsaidcircuit-changer and main-line circuit to their normal positions.

JOHN I. SABIN.

